From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2F56CCCD183 for ; Sat, 11 Oct 2025 09:31:09 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v7VvE-0008KN-8z; Sat, 11 Oct 2025 05:29:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v7VvB-0008KF-BN for qemu-devel@nongnu.org; Sat, 11 Oct 2025 05:29:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v7Vv0-0004pR-PV for qemu-devel@nongnu.org; Sat, 11 Oct 2025 05:29:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760174976; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9YHJvf8XqxyGAZw72MT6wARkf/KNahEtb+3o14TuVew=; b=L7qLu6ILyNya0Etie3D10FiN5FxRV/Gr5j/rpoCTuyg4UNh+YmvsQTbQvgqQasFbqfNIPK bIhqsWv3rS0Ti6BbXk0OsiymKf+WBwY09oMPTbFk+7jAY7QakazKw3CYKY9yiwp6sOrHPd ex52EpVbiDabTUrfUdbRAofd9qFVU+A= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-493-1AkC8Wf5Nx2hwcsD7_Y4Ag-1; Sat, 11 Oct 2025 05:29:35 -0400 X-MC-Unique: 1AkC8Wf5Nx2hwcsD7_Y4Ag-1 X-Mimecast-MFC-AGG-ID: 1AkC8Wf5Nx2hwcsD7_Y4Ag_1760174973 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3A568180045C; Sat, 11 Oct 2025 09:29:33 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.6]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1AFFF1800578; Sat, 11 Oct 2025 09:29:32 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 588D821E6A27; Sat, 11 Oct 2025 11:29:29 +0200 (CEST) From: Markus Armbruster To: Gerd Hoffmann Cc: qemu-devel@nongnu.org, Paolo Bonzini , Yanan Wang , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Fabiano Rosas , Eric Blake , "Dr. David Alan Gilbert" , Laurent Vivier , Marcel Apfelbaum , Zhao Liu , Eduardo Habkost Subject: Re: [PATCH v3] hw/uefi: add "info firmware-log" + "query-firmware-log" monitor commands In-Reply-To: <874is6fyl7.fsf@pond.sub.org> (Markus Armbruster's message of "Fri, 10 Oct 2025 19:36:36 +0200") References: <20251010071008.2555267-1-kraxel@redhat.com> <87ecrbj85s.fsf@pond.sub.org> <874is6fyl7.fsf@pond.sub.org> Date: Sat, 11 Oct 2025 11:29:29 +0200 Message-ID: <87h5w5dbwm.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.441, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Yet another thing... Markus Armbruster writes: > One more thing... or rather two. > > Markus Armbruster writes: > >> Gerd Hoffmann writes: >> >>> Starting with the edk2-stable202508 tag OVMF (and ArmVirt too) have >>> optional support for logging to a memory buffer. There is guest side >>> support -- for example in linux kernels v6.17+ -- to read that buffer. >>> But that might not helpful if your guest stops booting early enough that >>> guest tooling can not be used yet. So host side support to read that >>> log buffer is a useful thing to have. >>> >>> This patch implements both qmp and hmp monitor commands to read the >>> firmware log. >> >> So this is just for EDK2, at least for now. >> >>> Signed-off-by: Gerd Hoffmann >>> --- >>> include/monitor/hmp.h | 1 + >>> hw/uefi/ovmf-log.c | 265 +++++++++++++++++++++++++++++++++++++ >>> tests/qtest/qmp-cmd-test.c | 2 + >>> hmp-commands-info.hx | 14 ++ >>> hw/uefi/meson.build | 2 +- >>> qapi/machine.json | 23 ++++ >>> 6 files changed, 306 insertions(+), 1 deletion(-) >>> create mode 100644 hw/uefi/ovmf-log.c >>> >>> diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h >>> index ae116d9804a3..885c0ecd2aed 100644 >>> --- a/include/monitor/hmp.h >>> +++ b/include/monitor/hmp.h >>> @@ -178,5 +178,6 @@ void hmp_boot_set(Monitor *mon, const QDict *qdict); >>> void hmp_info_mtree(Monitor *mon, const QDict *qdict); >>> void hmp_info_cryptodev(Monitor *mon, const QDict *qdict); >>> void hmp_dumpdtb(Monitor *mon, const QDict *qdict); >>> +void hmp_info_firmware_log(Monitor *mon, const QDict *qdict); >>> >>> #endif >>> diff --git a/hw/uefi/ovmf-log.c b/hw/uefi/ovmf-log.c >>> new file mode 100644 >>> index 000000000000..89e27d916531 >>> --- /dev/null >>> +++ b/hw/uefi/ovmf-log.c >>> @@ -0,0 +1,265 @@ >>> +/* >>> + * SPDX-License-Identifier: GPL-2.0-or-later >>> + * >>> + * print ovmf debug log >>> + * >>> + * see OvmfPkg/Library/MemDebugLogLib/ in edk2 >>> + */ >>> + >>> +#include "qemu/osdep.h" >>> +#include "qemu/units.h" >>> +#include "qemu/base64.h" >>> +#include "qemu/target-info-qapi.h" >>> +#include "hw/boards.h" >>> +#include "hw/i386/x86.h" >>> +#include "hw/arm/virt.h" >>> +#include "system/dma.h" >>> +#include "monitor/hmp.h" >>> +#include "monitor/monitor.h" >>> +#include "qapi/error.h" >>> +#include "qapi/type-helpers.h" >>> +#include "qapi/qapi-commands-machine.h" >>> + >>> + >>> +/* ----------------------------------------------------------------------- */ >>> +/* copy from edk2 */ >>> + >>> +#define MEM_DEBUG_LOG_MAGIC1 0x3167646d666d766f /* "ovmfmdg1" */ >>> +#define MEM_DEBUG_LOG_MAGIC2 0x3267646d666d766f /* "ovmfmdg2" */ >>> + >>> +/* >>> + * Mem Debug Log buffer header. >>> + * The Log buffer is circular. Only the most >>> + * recent messages are retained. Older messages >>> + * will be discarded if the buffer overflows. >>> + * The Debug Log starts just after the header. >>> + */ >>> +typedef struct { >>> + /* >>> + * Magic values >>> + * These fields are used by tools to locate the buffer in >>> + * memory. These MUST be the first two fields of the structure. >>> + * Use a 128 bit Magic to vastly reduce the possibility of >>> + * a collision with random data in memory. >>> + */ >>> + uint64_t Magic1; >>> + uint64_t Magic2; >>> + /* >>> + * Header Size >>> + * This MUST be the third field of the structure >>> + */ >>> + uint64_t HeaderSize; >>> + /* >>> + * Debug log size (minus header) >>> + */ >>> + uint64_t DebugLogSize; >>> + /* >>> + * edk2 uses this for locking access. >>> + */ >>> + uint64_t MemDebugLogLock; >>> + /* >>> + * Debug log head offset >>> + */ >>> + uint64_t DebugLogHeadOffset; >>> + /* >>> + * Debug log tail offset >>> + */ >>> + uint64_t DebugLogTailOffset; >>> + /* >>> + * Flag to indicate if the buffer wrapped and was thus truncated. >>> + */ >>> + uint64_t Truncated; >>> + /* >>> + * Firmware Build Version (PcdFirmwareVersionString) >>> + */ >>> + char FirmwareVersion[128]; Note for later: FirmwareVersion is an array. >>> +} MEM_DEBUG_LOG_HDR; [...] >>> +static void handle_ovmf_log_range(GString *out, >>> + dma_addr_t start, >>> + dma_addr_t end, >>> + Error **errp) >>> +{ >>> + g_autofree char *buf = NULL; >>> + >>> + if (start > end) { >>> + return; >>> + } >>> + >>> + buf = g_malloc(end - start + 1); >> >> How big can this buffer become? See [*] below. >> >>> + if (dma_memory_read(&address_space_memory, start, >>> + buf, end - start, >>> + MEMTXATTRS_UNSPECIFIED)) { >>> + error_setg(errp, "firmware log: buffer read error"); >>> + return; >>> + } >>> + >>> + buf[end - start] = 0; >>> + g_string_append_printf(out, "%s", buf); >> >> This falls apart when the log contains '\0'. Suggest something like >> >> g_string_append_len(out, buf, end - start); >> >> or even better, the direct read Daniel suggested. >> >>> +} >>> + >>> +FirmwareLog *qmp_query_firmware_log(Error **errp) >>> +{ >>> + MEM_DEBUG_LOG_HDR header; >>> + dma_addr_t offset, base; >>> + FirmwareLog *ret; >>> + g_autoptr(GString) log = g_string_new(""); >>> + >>> + offset = find_ovmf_log(); >>> + if (offset == -1) { >>> + error_setg(errp, "firmware log: not found"); >>> + return NULL; >>> + } >>> + >>> + if (dma_memory_read(&address_space_memory, offset, >>> + &header, sizeof(header), >>> + MEMTXATTRS_UNSPECIFIED)) { >>> + error_setg(errp, "firmware log: header read error"); >>> + return NULL; >>> + } >>> + >>> + if (header.DebugLogSize > MiB) { >>> + /* default size is 128k (32 pages), allow up to 1M */ >>> + error_setg(errp, "firmware log: log buffer is too big"); >> >> [*] We limit the buffer to 1MiB. No objection to the size. >> >> What do you mean by "default" in "default size"? Is the size >> configurable in EDK2? >> >> Should we try to cope more gracefully with oversized log buffers? It's >> a ring buffer. What about silently reading the latest 1MiB then? >> Behaves just as if the ring buffer was 1MiB. >> >>> + return NULL; >>> + } >>> + >>> + if (header.DebugLogHeadOffset > header.DebugLogSize || >>> + header.DebugLogTailOffset > header.DebugLogSize) { >>> + error_setg(errp, "firmware log: invalid header"); >>> + return NULL; >>> + } >>> + >>> + base = offset + header.HeaderSize; >>> + if (header.DebugLogHeadOffset > header.DebugLogTailOffset) { >>> + /* wrap around */ >>> + handle_ovmf_log_range(log, >>> + base + header.DebugLogHeadOffset, >>> + base + header.DebugLogSize, >>> + errp); >>> + if (*errp) { >>> + return NULL; >>> + } >>> + handle_ovmf_log_range(log, >>> + base + 0, >>> + base + header.DebugLogTailOffset, >>> + errp); >>> + if (*errp) { >>> + return NULL; >>> + } >>> + } else { >>> + handle_ovmf_log_range(log, >>> + base + header.DebugLogHeadOffset, >>> + base + header.DebugLogTailOffset, >>> + errp); >>> + if (*errp) { >>> + return NULL; >>> + } >>> + } >>> + >>> + ret = g_new0(FirmwareLog, 1); >>> + ret->version = g_strdup(header.FirmwareVersion); FirmwareVersion is char[128]. g_strdup() copies until the first zero byte. I fear a malicious guest can set up its memory to make us allocate and copy a lot more than 127 bytes. Please use g_strndup(). >>> + ret->log = g_base64_encode((const guchar *)log->str, log->len); >>> + return ret; >> >> Note for later [**]: both ->version and ->log are non-null on success. >> >>> +} [...]